1. Field of the Invention
The present invention relates to an electronic paper display device and a method of manufacturing the same, and more particularly, to an electronic paper display device having a high contrast ratio and high reliability and requiring low driving voltage, and a method of manufacturing the same.
2. Description of the Related Art
A shift in information exchange and sharing methods is currently in demand, corresponding to the information society requiring a new paradigm. To meet this demand, the development of technologies associated with flexible electronic paper has recently been accelerated and has now entered the phase of commercial development.
Compared with existing flat display panels, an electronic paper display requires relatively low manufacturing costs, and is far superior in terms of energy efficiency since it is operable even with a very low level of energy since backlighting or continuous recharge is unnecessary. Furthermore, the electronic paper enables a high definition display, provides a wide viewing angle, and is equipped with a memory function that retains the display of letters (characters) even when not powered. The above-described advantages make electronic paper applicable in a wide variety of technical fields, such as electronic books having paper-like sheets and moving illustrations, self-updating newspapers, reusable paper displays for mobile phones, disposable TV screens, and electronic wallpaper. There is a massive potential market for such electronic paper.
A technical approach for the implementation of electronic paper may be roughly divided into four methods: a twist-ball method, an electrophoretic method, a quick response-liquid power display (QR-LPD) method, and a cholesteric liquid crystal display method. Here, the twist ball method involves rotating spherical particles, each having upper and lower hemispheres having opposite electrical charges and different colors, by using an electric field. As for the electrophoretic method, colored charged particles mixed with oil are trapped in micro-capsules or micro-cups, or charged particles are made to respond to the application of an electric field. The QR-LPD method uses charged powder. The cholesteric liquid crystal display method uses the selective reflection of cholesteric liquid crystal molecules.
As for the twist-ball method, cells are filled with a transparent medium, and twist balls, each having opposite electrical charges and is colored with different colors, for example black and white, are disposed in the transparent medium. Each twist ball, when receiving voltage, rotates such that its part, having an opposite polarity to the received electric charge, faces the front. In such a manner, black and white are displayed.
In general, the twist balls are disposed inside an elastomer matrix. Thus, the arrangement of the twist balls is not consistent, and it is difficult to attach a driving circuit thereto.